Re: [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks

[Sean Christopherson <seanjc@xxxxxxxxxx>]

On Fri, Sep 17, 2021, Peter Zijlstra wrote:
> On Thu, Sep 16, 2021 at 09:37:43PM +0000, Sean Christopherson wrote:
> So I don't mind exporting __static_call_return0, but exporting a raw
> static_call is much like exporting a function pointer :/

Ya, that part is quite gross.

> > The unregister path would also need its own synchronize_rcu().  In general, 
> > I
> > don't love duplicating the logic, but it's not the end of the world.
> > 
> > Either way works for me.  Paolo or Peter, do either of you have a 
> > preference?
> 
> Can we de-feature kvm as a module and only have this PT functionality
> when built-in? :-)

I agree that many of the for-KVM exports are ugly, especially several of the
perf exports, but I will fight tooth and nail to keep KVM-as-a-module.  It is
invaluable for development and testing, and in the not-too-distant future there
is KVM-maintenance related functionality that we'd like to implement that relies
on KVM being a module.

I would be more than happy to help explore approaches that reduce the for-KVM
exports, but I am strongly opposed to defeaturing KVM-as-a-module.  I have a few
nascent ideas for eliminating a handful of a random exports, but no clever ideas
for eliminating perf's for-KVM exports.